Brake control means



Dec. 29, 1942. E. P. SEXTON BRAKE CONTROL MEANS Filed Aug. 28, 194i 2 Sheets-Sheet 1 INVEINTOR EVERETT P. EEXTON ATTORNEY .Dec.29 ,1942. E. RSEXTON 2,306,505

BRAKE CONTROL MEANS Filed Aug. 28, 1941 2 Sheets-Shet 2 INVENTOR EVERETT E EEXTON B MQM ATTORNEY Patented Dec. 29, 1942 BRAKE CONTROL MEANS Everett P. Sexton, East McKeesport, Pa., assignor to The Westinghouse Air Brake Company, Wilmerding, Pa., a corporation of Pennsylvania Application August 28, 1941, Serial No. 408,618

12 Claims.

This invention relates to brake control means for vehicles, such as railway cars and trains, and has particular relation to apparatus responsive to the speed of rotation of a vehicle wheel as well as to the rate of change of rotational speed of the wheel for automatically controlling the degree of application of the brakes associated with the wheel in a manner to prevent sliding thereof.

It is a well known fact that the coefficient of friction between the brake shoes and the rim of railway car wheels increases as the speed of the car or train decreases. In the past it has been customary therefore for the operator of a train to manually decrease the degree of application of the brakes on the cars of the train, as the speed of the train reduces, in order to prevent application of the brakes on the wheels to a sufficient degree to cause locking of the wheels and a consequent sliding thereof. More recently, speed governors of various types have been proposed and employed for automatically efiecting a reduction in the degree of application of the brakes associated with the wheels of a train as the speed of the train decreases.

Various devices have also been proposed and provided whereby to recognize the slipping condition of a car wheel and to cause an automatic and rapid release of the brakes associated with the slipping wheels, so as to cause restoration of the slipping wheels back to a speed corresponding to car speed without permitting the wheel to actually decelerate to a locked condition and slide.

The terms slipping and sliding as applied to vehicle wheels in the present application are not synonymous. The term slipping refers to the rotation of a vehicle wheel at a speed less than a speed corresponding to car speed at a given instant and the term sliding refers to the dragging of a vehicle wheel along a road surface or rail in a locked condition.

When a car wheel slips, it decelerates at an abnormally rapid rate never attained while the wheel is not slipping. The registration of the rotativerdeceleration of the vehicle wheel at a rate exceeding a certain rate never attained normally while the wheel is not slipping is thus positive indication of the slipping condition of the vehicle wheel.

It is an object of my present invention to provide a brake control equipment for vehicles, such as railway cars and trains, including a novel type of device which is responsive to the actual speed of rotation of a vehicle wheel and also to the rate of..change .of rotational'speed of the wheel whereby to cause the degree of application of the brakes on the car or train to be controlled normally, according to variations in the speed of the train and, also, in the event of slipping of individual car wheels or car wheel units, to effect instantaneously a rapid reduction in the degree of application of the brakes associated with the individual wheels so as to prevent the sliding thereof.

It is another object of my invention to provide a vehicle brake control equipment of the type in which the degree of application of the brakes is automatically decreased to a certain low degree as the speed of the vehicle decreases, further characterized by means automatically effective to cause an increase in the degree of application of the brakes from the certain low degree when the vehicle comes to a complete stop to thereby insure an adequate degree of application of the brakes sufiicient to hold the car or train on any grade encountered in service.

It is another object of my invention to provide a novel type of device for registering the speed of a rotary element, such as a vehicle wheel.

It is another object of my invention to provide a novel type of device for registering the. rate of change of rotational speed of a rotary element.

It is still another object of my invention to provide a novel type of device for registering both the speed of rotation of a rotary element and its rate of change of speed.

The above objects and other objects of my invention which will be made apparent hereinafter, are attained by equipment subsequently to be described and shown in the accompanying drawings, wherein Fig. 1 is a diagrammatic view, showing in simplified diagrammatic form brake control equipment embodying my invention and illustratively shown as applied to a four-wheel car truck, and

Fig. 2 is an enlarged vertical sectional view of one of the novel governor devices shown in Fig. 1.

Description of equipment .20 at the brake valve.

The brakes associated with the wheels I i may be of the conventional clasp type in which the shoes are arranged so as to be applied and released through intervening brake levers and brake rigging, not shown, in response to the supply of fluid under pressure to and the release of fluid under pressure from brake cylinders l2. In the drawings each of the brake cylinders is adapted to operate the brakes associated with the wheel and axle assembly in vertical alignment therewith. It should be understood however, that any desired number of brake cylinders may be provided.

For the purposes of my present invention, any suitable type of apparatus may be provided whereby the operator stationed on one unit or car of a train may control the supply and the release of fluid under pressure to and from the brake cylinders on all cars. For simplicity, I have illustrated a simple straight-air type of fluid pressure brake control equipment comprising two train pipes l3 and M, hereinafter referred to as the supply pipe and the control pipe respectively; a reservoir l5, hereinafter referred to as the main reservoir, which is constantly connected to the supply pipe l3 as through a branch pipe l6; and a manually operated brake valve I1, illustrated as of the self-lapping type, which is connected by branch pipes l8 and is to the supply pipe l3 and control pipe hi respectively.

The fluid pressure brake control equipment may further comprise a differential relay 2| which is connected by a branch pipe Ma to the control pipe M and which is responsive to the fluid pressure established in the control pipe E4 to cause fluid under pressure to be supplied from a branch pipe |3a of the supply pipe to a pipe 22 having branches leading to the brake cylinders |2 on the corresponding car. The pipe 22, as shown in Fig. 1, is provided with two branches one of which leads to the brake cylinders l2 for the wheel truck shown in the drawings and a second branch extending in the right-hand direction and leading to the brake cylinders for the wheel truck, not shown, at the opposite end of the car.

Each branch of the pipe 22 is provided with two branches 22a and 2% leading respectively to the two brake cylinders of the corresponding wheel truck.

Interposed in each of the branch pipes 22a and 22b is a magnet valve device 24 the purpose of which will be explained hereinafter.

Associated with each of the brake cylinders l2 and responsive to the pressure therein is a fluid pressure operated switch device 25, hereinafter referred to as the pressure switch.

The brake valve I! is of the self-lapping type described and claimed in Patent 2,042,112 to Ewing K. Lynn and Rankin J. Bush. Since reference may be had to this patent for a detailed description of the structure and operation of the brake valve, it will be described only functionally herein. With the brake valve handle Ila in normal brake release position, communication is established by the brake valve through which fluid under pressure is exhausted from the control pipe l4 through an exhaust port and pipe When the brake valve handle Ila is shifted in a horizontal plane out of its brake release position into a so-called application zone, the brake valve mechanism supplies fluid under pressure from the supply pipe l3 to the control pipe I4, the pressure established in the control pipe being substantially proportional to the degree of displacement of the brake valve handle out of its brake release position.

If the pressure in the control pipe I4 tends to reduce for any reason, such as leakage, the brake valve mechanism operates automatically to continue to supply fluid under pressure thereto to maintain a pressure in the central pipe corresponding to the position of the brake valve handle. This pressure-maintaining feature of the brake valve will be referred to hereinafter.

The diflerential relay valve device 2| is of the type described and claimed in Patent 2,140,624 to E. E. Hewitt. Since reference maybe had to the patent, the device is shown only in outline form and will be described only briefly herein. The differential relay valve device 2| comprises a relay valve section 28, a diaphragm section 29, and a magnet valve section 30. The relay valve section 28 comprises a self-lapping relay valve apparatus including a supply valve and a release valve. The supply valve controls the supply of fluid under pressure from pipe |3a to the brake cylinder pipe 22. The release valve controls the exhaust of fluid under pressure from the brake cylinder pipe 22 to atmosphere.

The diaphragm section 29 comprises a plurality of coaxially disposed diaphragms of successively increasing or decreasing effective pressure areas, the larger of the diaphragms being adjacent the relay valve section 28 and subject on one side to the pressure in the brake cylinder pipe 22.

Fluid under pressure from the control pipe M and its branch pipe Ma is supplied selectively to the chambers, formed between two successive diaphragms, under the control of corresponding magnet valve devices 3|, 32 and 33 of the magnet valve section 30.

A chamber formed at the outer face of the smallest diaphragm is constantly subject to the pressure in the control pipe I4.

The diaphragms of the diaphragm section 29 are effective individually or collectively to exert a force to operate the valves of the relay valve section 28 to cause a supply of fluid under pressure to the brake cylinder pipe 22, the valves being restored to a lapped condition when the force of the brake cylinder pressure on the one side of the largest diaphragm balances the force exerted in the opposite direction by the control pipe presure acting on the diaphragms. Thus varying ratios between the pressure established in the brake cylinders and that established in the control pipe l4 may be attained depending upon the relation or ratio between the effective pressure areas of the several diaphragms. In the following description of the operation of the equipment it will be assumed that there are four diaphragms having respective effective pressure areas of 10, 8, 6 and 4 square units of area.

It will be understood, therefore, without further description that when the magnet windings of both magnet valves 32 and 33 are energized while that of the magnet winding of the magnet valve 3| is deenergized, the differential relay 2| is conditioned to supply fluid at a pressure substantially equal to that in the control pipe to the brake cylinders.

When only the magnet winding of the magnet valve 32 is energized, the differential relay is conditioned to supply fluid to the brake cylinders at a pressure which is only eighty percent of that established in the control pipe.

When the magnet windings of all of the magnet valves are deenergized, the differential relay 2| is conditioned to supply fluid to the brake cylinders at a pressure which is sixty percent of that established in the control pipe.

When the magnet winding of only the magnet valve 3| is energized, the diiierential relay 2| is conditioned to supply fluid at a pressure to the brake cylinders at pressure which is only forty percent of that established in the control pipe.

It should be understood that the actual pressure in the brake cylinders will vary in response to variation of the control pipe pressure but that the ratio of the pressure in the brake cylinders and that in the control pipe never varies for a given condition of the differential relay 2|.

The magnet valves E i are identical and accordingly only one is shown in section and will be described. The magnet valve 24 is of the double beat type having a double beat valve 35 contained in a chamber 36 and biased to an upper seated position by a coil spring 3'! contained in a chamber 33. Upon energization of a magnet winding or solenoid 39 a plunger 4| is actuated downwardly to shift the double beat valve 35 to r, lower seated position.

In its upper seated position, valve 35 estab- 1 lishes communication from one section of the branch pipe 22a or 222) to the other section leading to the corresponding brake cylinder by way of the chambers 38 and 36. In its lower seated position, valve 35 closes such communication and establishes an exhaust communication connect ing the chamber 36 to a chamber 32 constantly pen to atmosphere through a relatively large exhaust port 43.

Thus, when the magnet winding 39 of the magnet valve 24 is deenergized, fluid under pressure may be supplied to the corresponding brake cylinder l2 and released therefrom by operation of the diiierential relay 2 I. When the magnet winding 39 of the magnet valve 24 is energized, the supply of fluid under pressure to the brake cylinder i2 is cut oh and fluid under pressure is released at a rapid rate to atmosphere through the exhaust port d3 independently of the differential relay 2 i.

The pressure switches 25 are preferably of the snap-acting type described and claimed in Patent 2,696,492 to E. E. Hewitt. Since reference may be had to the patent just mentioned, a brief functional description is believed to be sufficient for purposes of the present application. Each of the pressure switches comprises a movable contact a and two stationary contacts I) adapted to be bridged by the movable contact a. The movable contact a is biased to an open position out of engagement with the associated contacts b as long as the pressure in the corresponding brake cylinder l2 remains below a certain low pressure such as five pounds per square inch. When the pressure in the brake cylinder exceeds such critical pressure, the contact a is snapped suddenly into engagement with the associated contacts I} which position will hereinafter be referred to as the closed position of the pressure switch. Thereafter, when the pressure in the brake cylinder reduces below five pounds per square inch, the contact a is snapped suddenly to the open position.

In accordance with my invention, the brake control equipment shown in Fig. 1 further comprises a so-called governor device Q5 and a plurality of relays 56, i1, 48, 49 and 55 in connection with one of the wheel units, illustrated as the left-hand wheel unit of the wheel truck shown,

and a governor device 45 and relays 45, 41, 48

and 49 in connection with each remaining wheel unit of a particular car.

Referring to Fig. 2, each governor device comprises a casing including a portion formed to provide a fluid reservoir or chamber 53, a portion for receiving a pump 54 shown as of the centrifugal type, and a laterally extending portion on which two vertically extending tubes 55 and 53 of glass or porcelain material are supported. The glass tubes 55 and 56 may be cemented at their lower ends in a metallic flange 51 adapted to be secured as by a plurality of screws 58 to the remaining portion of the casing containing the reservoir 53 and pump 54. The reservoir 53 is provided with suitabl filling opening having a screw plug 53 and a drain opening having a screw plug 59.

In accordance with my invention, fluid or high specific gravity, such as mercury, is admitted through the filling opening to fill the reservoir and pump chamber substantially to the level indicated.

The pump 55 may comprise a plurality of blades 6! secured to a rotary shaft 52 which extends to the exterior of the casing and Which is adapted to be rotated in accordance with the speed or rotation of the corresponding wheel or wheel unit by any desired type of drive mechanism. Upon rotation of the blades 5!, mercury is expelled from the pump chamber into a laterally extending passage 65 and rises in the tubes 55 and 5% which are open at the lower ends thereof to the passage 65. The level to which the mercury in the tubes 55 and 55 is raised corresponds substantially to the rotational speed of the vehicle wheel driving the pump 5%. That is, the mercury rises in the tubes until the weight of the column in each tube balances the force exerted by the pump which is in turn substantial- 1y proportional to the rotational speed of the vehicle Wheel driving the pump.

The tube 5t is open at its lower end through a relatively large port 66 whereas the lower end of the tube 55 is open to the passage 65 through a relatively smaller or restricted port 67. The nature and the design of the ports 55 and 5'! is such that the level of the mercury in the tube 55 is adjusted instantaneously in accordance with the rotational speed of the vehicle wheel driving the pump whereas the level of the mercury in the tube 55 is adjusted according to the change in the rotational speed of the vehicle wheel driving the pump only if the rate of change of speed does not exceed a certain value, such as eight miles per hour per second.

In view of the fact that a vehicle wheel never attains, a rate of deceleration of eight miles per hour per second unless the wheel is slipping, it will be seen that as long a the corresponding vehicle wheel does not slip, the level or height of the column in the two tubes will rise and fall in unison with variations in wheel speed. If the wheel driving the pump should slip, however, the rate of deceleration of the wheel greatly exceeds eight miles per hour per second and thus the height of the mercury column in the two tubes does not fall in unison, the column in the tube 56 falling rapidly in correspondence with the reduction in speed of the wheel whereas the height of the mercury column in tube 55 falls merely in accordance with a rate of deceleration of eight miles per hour per second as limited by the size of the restricted port or choke 51.

In order to prevent the development of pressure in the upper ends ofthetubes 55 and 56 as the mercury rises in the tubes, each of the tubes is provided with a breather port or opening 69.

Suitably sealed 01' cemented in openings provided in the wall of the tube 55 are a plurality of vertically spaced contact H, 12, 13, i4 and 75. Also cemented in the tube 55 at the level of the contact H is an additional contact 16.

The contacts H to 15 may be vertically spaced in any desired position so as to be engaged 01' contacted by the mercury within the tube at corresponding different rotational speeds of the vehicle wheel. For purposes of illustration, it will be assumed that the level of the mercury in the tube 55 reaches the contact H when the wheel rotates at a speed corresponding to two miles per hour, reaches the level of the contact 12 when the wheel rotates at a speed of twenty miles per hour, reaches the level of the contact 13 when the wheel rotates at a speed of forty miles per hour, reaches the level of the contact 74 when the wheel rotates at a speed of sixty-five miles per hour and reaches the level of contact 15 when the wheel rotates at a speed of ninety miles per hour.

Also suitably cemented in holes provided in the walls of the tube 56 are a series of vertically spaced contacts 82, 83, 84, 85 and 86.

The contact 86 is at the same level as the con-- tacts I i and 16 of the tube 55 and is thus engaged by the mercury in the tube 56 when the wheel rotates at a speed of two miles per hour.

The contact 82 is so positioned vertically in the tube 56 as to be reached by the mercury in the tube whenever the speed of rotation of the wheel reaches eighteen miles per hour. Contacts 83, 84 and 85 are so positioned as to be reached by the level of the mercury in the tube when the wheel reaches speeds of thirty-seven, sixty and eighty-five miles per hour respectively.

The reason for the difference in the elevational positions of the contacts 12 to 75 with respect to that of the contacts 82 to 85 will be made apparent hereinafter.

The contact 76 and 86 of each governor device are connected by a corresponding wire 9| including the contacts of a corresponding pressure switch 25 to a bus wire 93 extending the length of the car to which the positive terminal of a source of current such as a storage battery 94 is connected. The negative terminal of the battery 94 is connected to a similar bus wire 95 which extends the length of the car. The wires 93 and 95 are hereinafter designated the positive battery wire and the negative battery wire respectively.

Relays 46 to 59 are conventional or standard relays of the neutral type. Each relay has a single contact, known as a back-contact, which is biased to a closed position when the winding of the relay is deenergized and which is actuated to an open position when the winding of the relay is energized.

The windings of the relays 46 is serially ar ranged in a wire 96 which is connected at one to the contact 85 and at the other end to a branch wire 95a of the negative battery wire 95.

The winding of the relay 41 is serially arranged in a wire 91 which is connected at one end to the contact 84 and at the opposite end to the wire 95a.

The winding of the relay 48 is serially arranged in a wire 98 connected at one end to the contact 83 and at the opposite end to the wire 95a.

The winding of the relay 49 is serially arranged in a wire 99 connected at one end to the contact 82 and at the other end to the wire 95a.

The winding of the relay 50 is serially arranged in a wire I69 connected at one end to the contact 12 and at the other end to the wire 95a.

It will now be apparent that when the mercury in the tube 56 connects contact 89 to the contacts 82, 83, 84 and 85, a circuit is completed for energizing the windings of the relays 49, 48, 4'! and 46, respectively. Similarly, when the mercury in the tube 55 connects contacts 16 and '12, the winding of the relay 50 is energized.

The contact H of one governor, illustrated as the left-hand governor in Fig. l, for each car is connected by a wire l0! including in series relation therein the back-contact of the relay 59 and the winding of the magnet valve 3| of the differential relay valve device 2| to a branch wire 95b of the negative battery wire 95. It will thus be seen that when the contact oi the relay 59 is in its dropped-out or closed position when the level of the mercury column in tube 55 is above the contact H, the circuit is completed for energizing the magnet winding of the magnet valve 3|, assuming that the pressure switch is in closed position.

The contact 73 of the left-hand governor is connected by a wire l62 including in series relation therein the magnet winding of the magnet valve 32 of the differential relay valve device 2| to the branch wire 9%- of the negative battery wire 95. If the corresponding pressure switch 25 is closed, the connection of the contacts H and 13 by the mercury column within the tube is thus effective to complete a circuit for energizing the magnet winding of the magnet valve device 32.

The contact 74 of the left-hand governor device 45 is connected by a wire Hi3, including in series relation therein the magnet winding of the magnet valve device 33 of the differential relay valve 25, to branch wire of the negative battery wire 95. Thus, if the corresponding pressure switch 25 is closed, the connection of the contacts H and M by the mercury in the tube 55 is effective to complete a circuit for energizing the magnet winding of the magnet valve 33.

The contacts l2, 13, T4 and '15 of each governor device 45 are connected by wires H2, H3, H4 and H5 including in series relation therein the back-contact of the relay 49, 49, 4? and 46 respectively, to a common wire l l 6 that is, in turn, connected to one terminal of the magnet winding 39 of the magnet valve 24 for the corresponding wheel unit. The other terminal of the magnet winding 39 of the magnet valve 24 is connected by a wire I H to the negative battery wire 95.

It will thus be seen that if the height of the mercury columns in the two tubes 55 and 56 is the same and drops in unison, the circuit will not be completed for energizing the magnet winding 39 of the magnet valve 24 associated therewith. If, however, the height of the mercury column in the tube 56 drops at a faster rate than that in the column in the tube 55, as is the case when the corresponding wheel or wheel unit slips, the contacts of one or more of the relays 46, 41, 48 and 49 will be restored to the dropped-out or closed position thereof while the mercury in the tube 55 still connects the contacts 16 to one or more of the contacts 75, 14, 13 and '12.

A circuit for energizing the magnet winding 39 of the magnet valve 24 is thus established when the wheels of the corresponding wheel unit slip.

Operation of equipment Let it be assumed that a car or train equipped with the brake control equipment shown in Fig. 1 is traveling along the road under power, with the brakes released, at a speed in excess of ninety miles per hour and that the operator desires to bring the car or train to a stop. To do so the operator first shuts off the propulsion power and then shifts the brake valve handle Ila out of its brake release position an amount corresponding to the desired degree of application of the brakes.

The control pipe I4 is accordingly charged to a corresponding pressure, for example fifty pounds per square inch. Thedifferential relay valve device 2| which is conditioned in the manner presently described operates in response to the pressure established in the control pipe to cause fluid under pressure to be supplied to the brake cylinders [2, the ratio of the pressure established in thebrakecylinders with respect to the pressure established in the control pipe depending upon the condition of the diiierential relay 2|.

With the vehicle traveling in excess of ninety miles per hour, circuits are accordingly completed for energizing the magnet windings of the magnet valves 32 and 33 of the differential relay 2% upon the closure of the pressure switch associated with the corresponding control governor #5. As previously indicated, the pressure switch 25 closes Whenever the pressure of the fluid supplied to the brake cylinders exceeds five pounds per square inch. Thus, substantially at the instant that the application of the brakes is initiated, the differential relay valve device 2| is automaterially conditioned in accordance with the speed of travel of the car or train.

It will be understood that the magnet windings of the magnet valves 32 and 33 are energized because the mercury column in the tube 55- connects the contact 16 to the contacts 14 and 13 re spectively, with the car or train traveling at a speed in excess of ninety miles per hour. At the same time, the mercury column in the tube 55 connects the contacts 72 and H to contact 16. Thus the winding of the relay is energized and its back-contact actuated to its open position so that although the mercury column in the tube connects the contact H to the contact 76 the circuit for energizing the magnet winding of the magnet valve 3| is interrupted at the contact of the relay 50. 7 It will accordingly be seen that upon application of the brakes under the circumstances assumed, the differential relay valve device 2| is conditioned to cause fluid under pressure to be supplied to the brake cylinders [2 on the car to establish a pressure therein corresponding or substantially equal to the pressure established in the control pipe l4 so that the brakes associated with the vehicle wheels are applied to a corresponding degree.

The pressure established in the brake cylinders It remains constant thereafter, assuming that the operator does not change the pressure in the control pipe and that none of the wheels slip, until such time as the speed of the vehicle or the car or train reduces below sixty-five miles per hour-at which time the mercury column in the tube 55 descends below the contact 14 and thus interrupts the circuit for energizing the magnet winding of. the magnet valve 33 of the differential relay 2|.

With the magnet winding of the magnet valve 32 thus energized and the magnet windings of the magnet valves 3| and 33 deenergized, the condition of the difierential' relay 2| is so changed as to eiiect a reduction of the pressure in the brake cylinders at a controlled rate until the pressure remaining in the brake cylinders attains a value which is eighty percent of that established in the control pipe I4. The pressure in the brake cylinders is not reduced instantaneously to eighty percent of the pressure in the control pipe when the speed of the car or train reduces below sixty-five miles perhour, but is reduced at a controlled rate so that actually the pressure in the brake cylinders is not reduced to eighty percent :of that in the control pipe until some time after the instant that the speed of the car or train reduces below sixty-five miles per hour.

When the speed of the car or train reduces below forty miles per hour and the level of mercury column in tube 55 descends correspondingly below the contact 13, the circuit for energizing the magnet winding of the magnet valve 32 of the differential relay 2| is interrupted. Differential relay 2| is thus again varied in condition so as to efiect a further reduction of the pressure in the brake cylinders on the car to a value which is sixty percent of that established in the control pipe. As in the previous instance, the reduction of the pressure in the brake cylinders does not take place instantaneously but at a controlled rate so that the pressure in the brake cylinders does not reduce to a value of sixty percent of the control pipe pressure until some time after the instant that the speed of the car or train reduces below forty miles per hour.

When the speed of the car or train reduces below twenty miles per hour in response to the application of the brakes so that the height of the mercury column in the tube 55 descends correspondingly below the contact 12, the circuit for energizing the relay 5!) is interrupted. The backcontact of the relay 5% is thus restored to its dropped-out or open position completing the circuit for energizing the magnet winding of the magnet valve 3| of the differential relay 2|.

The condition of the difierential relay 2i is thus changed so as to cause the differential relay to effect a further reduction of the pressure of the brake cylinders on the car to a value which is only forty percent of that established in the control pipe M. As in previous instances, the change in the condition of the differential relay 2| causes reduction of brake cylinder pressure at a controlled rate, the ultimate value to which the pressure in the brake cylinder is reduced being attained some time after the instant that the speed of the car reduces below twenty miles per hour.

When the car or train comes to a complete stop and level of the mercury column in the tube descends correspondingly below the contacts ii and iii, the circuit for energizing the magnet winding of the magnet valve 3| oi the difierential relay 2| is interrupted. The differential relay 2| is thus restored to a condition for establishing a pressure in. the brake cylinder which is sixty percent of that established in the control pipe Ml, The differential relay 2| accordingly operates to supply fluid under pressure to the brake cylinders to effect a corresponding increase of the pressure therein.

It will thus be seen that the degree of applicaticn of the brakes on the wheels of the car is automatically reduced in steps to a certain low value and then, when the car comes to a complete stop, is again increased to a certain value higher than the certain low value in order to establish an adequate degree of brake application to hold the car or train against creepage on a grade.

Obviously, the operator may vary the pressure in the control pipe hi while a car or train is being brought to a stop, in which case the pressure in the brake cylinders l 2 will be correspondingly varied by operation of the differential relay 2|. However, for any particular speed range or condition of the differential relay 2 i, the ratio between the pressure established in the brake cylinders and that in the control pipe remains the same.

When it is desired to release the brakes prior to again starting the car or train, the operator merely restores the brake valve handle Ila to its brake release position, The pressure in the control pipe i4 is accordingly reduced to atmospheric pressure and the differential relay 2| on each car is accordingly operated to exhaust fluid under pressure fromv the brake cylinders of that car to eiiect complete release of the brakes.

When the fluid pressure in the brake cylinders reduces below five pounds per square inch, the

pressure switch 25 associated with each brake cylinder is restored to its open position. Thus until the brakes are again applied, the magnet windings of the magnet valves 3|, 32 and 33 of the relay valve device 2| cannot be energized regardless of the subsequent speed of travel of the car or train. Thus unnecessary drainage of current from battery 94 is prevented. Although I have shown a pressure switch for each brake cylinder obviously only one pressure switch may be used to control the connection of wire 9| from each governor to the positive battery wire 93. Moreover such pressure switch may be controlled according to the pressure in the control pipe instead of brake cylinder pressure.

In the previous operation it was assumed that none of the wheels on the car slipped. In the event that the wheels of one or more wheel units on the car begin to slip during an application of the brakes a further operation occurs which will now be described. Let it be assumed that the wheels H of the right-hand wheel unit in Fig. 1 begin to slip when the application of the brakes is initiated while the train is traveling in excess of ninety miles per hour. In such case the level of the mercury column in the tube 55 of the corresponding governor device 25 descends rapidly to below the contact 85 while, due to the restricted port 61 at the bottom of the tube 55, the level of the mercury column in the tube 55 descends at a lesser rate and thus remains above the contact T5 for a time. Since contacts 15 and 85 are separated in level by a difference corresponding to five miles per hour, it will be apparent that substantially at the instant that the wheels begin to slip. the contact of the relay 46 is restored to its dropped-cut or closed osition due to the interruption of the energizing circuit for the magnet winding for the rela 46 and a circuit is therebv completed for energizing the magnet winding 39 of the corresponding magnet valve 34. This circuit extends from the ositive battery wire 93 by way of the Wire ill including the contacts 01' the pressure switch 25, contact 6, the mercury column in the tube 55. contact l5. wire I 15 includin the back-contact of the relay 5, wire I I6, magnet winding 39 of the magnet valve 24 and wire H! to the negative battery wire 95.

The magnet valve 24 corresponding to the slipping wheels is accordingly operated to successively cut-oft communication through the branch pipe 22b to the brake cylinders 12 and effect a rapid exhaust of fluid under pressure from the brake cylinders.

Due to the instantaneous and rapid reduction of the pressure in the brake cylinders applying the brakes on the slipping wheels, the wheels promptly cease to decelerate at a slipping rate and begin to accelerate back toward a speed corresponding to car speed.

In most instances, the circuit for energizing the magnet winding 39 of the magnet valve 24 will be maintained as the speed of the slipping wheel reduces due to the fact that the mercury column in the tube 56 drops so much faster than the mercury column in the tube 55 that the mercury column in the tube 56 will descend below the next lower contact, such as the contact 84, before the mercury column in tube 55 descends below the preceding contact '!5 in the tube 55. Thus, although the mercury columns in the two tubes may reduce below the contacts 1'5 and 85, the circuit for energizing the magnet winding 39 of the magnet valve 24 will be maintained by way of contact 74 and wire I 14 including the back-contact of the relay 41, the magnet winding of which has previously been deenergized due to level of the mercury column in the tube 56 descending below the contact 84.

If, however, the level of the mercury column in tube 56 does not descend below the next lower contact before the height of the mercury column in the tube 55 descends below the preceding upper contact in the tube 55, it may happen that the circuit for energizing the magnet winding 39 of the 1 magnet valve 25 will be momentarily deenergized and then reenergized due to the continuing fa l of the mercury columns.

It will be apparent, however, that if a suflicient number of contacts are provided in the tubes, and corresponding relays also provided operating similarly to the relays 46, 41, 48 and 49, the magnet winding 39 will be energized continuously during the slipping interval. I have shown only a relatively few number of contacts in the tubes for simplicity but it will be understood that any desired number may be provided. For example, a sufficient number of contacts may be provided in the tubes 55 and 56 to correspond to intervals of ten miles per hour in the speed of the corresponding wheels instead of the illustrated speed intervals.

Upon the acceleration of the slipping wheels back toward the corresponding car speed, the level of the mercury column in the tube 56 is rapidly raised whereas the level of the mercury column in tube 55 is less rapidly raised due to the restricted ort 61. It will thus be apparent that sometime before the slipping wheels are restored fully to a speed corresponding to car speed and while they are accelerating back toward car speed, the level of the mercury columns in the two tubes 55 and 55 will be the same. The height of the mercury column in the tube 56 may even rise above that of the mercury column in the tube 55. In any case, whenever the two mercury columns are substantially the same height or whenever the merury column in tube 56 is higher than that in tube 55 it is im ossible for any of the several circuits to be established through the contacts of the relays 46. 41, 48 and 49 to efiect energization of the magnet winding 39 of the magnet valve 24. Thus. the magnet winding 39 will be deenergized and the magnet valve returned to its position restoring communication through the pipe 22b. Fluid will accordingly be resupplied to the brake cylinder l2 to establish a pressure therein determined 'by the condition of the difierential relay 2|.

It should be apparent that if, after the speed of the car is reduced below ninety miles per hour and is still above sixty-five miles per hour, a slipping of the wheels again occurs, the descent of the mercury column in tube 56 below contact 84 while the mercury column in the tube 55 remains above the contact 74 will complete a circuit for energizing the magnet winding of the magnet valve 24 to effect an instantaneous and rapid exhaust of the fluid under pressure from the brake cylinder Similarly, if slipping of the wheels occurs when the car is traveling at a speed between sixty-five and forty miles per hour, the descent of the Inercury column in tube 55 below the contact 83 while the mercury column in the tube 55 remains above the contact 13 establishes a circuit by way of the back-contact of the relay 43 for energizing the magnet winding 35 or" the magnet valve 2t.

Similarly, if slipping of the wheels occurs when the car is traveling at a speed less than forty and greater than twenty miles per hour, the descent of the mercury column in the tube 56 below the contact 82 while the mercury column in the tube 55 remains above the contact 12 causes a circuit to be established by way of the contact of the re lay 49 for energizing the magnet winding 39 of the magnet valve 24.

The operation of the governor 45 controlling the magnet valves 3 i, 32 and 33 of the differential relay 25 in the event that the corresponding wheels slip is the same as that just described for the governor oi right-hand wheel unit. Due to the reduction in the speed of the slipping wheels, however, the level of the mercury column in the tube 55 may reduce momentarily below the level corresponding to the actual speed of travel of the car. However, since it is almost instantly restored to the level corresponding to the speed of the car the momentary change in the condition of the diiierential relay 2? which might thus occur is not objectionable.

Although the wheel truck at the opposite end of the car to that shown in Fig. l is not shown, it will be understood that the brakes associated with each wheel unit of such truck are adapted to be controlled in accordance with the speed of the car by operation of the differential relay 25. It will also be understood that the governor device 45 for each of the wheel units of such truck operates in exactly the same manner as described for the right-hand wheel unit in Fig. l. to effect auto-- matically the instantaneous and rapid release of the brakes when the wheels of a wheel unit begin to slip for the purpose of preventing the sliding of the wheels.

While I have shown a magnet valve 24 for controlling the supply and release of fluid under pressure to and from only one brake cylinder, it will. be obvious that one magnet valve 24 may be arranged to control the supply and release of fluid under pressure to from all the brake cylinders of a single wheel truck or plurality of wheel A trucks. Moreover the several governor devices may be arranged in parallel so that the single mag et valve may be controlled by any one go ernor device it of a plurality on a car.

Summary Summarizing, it will be, seen that I have d sclosed a novel equipment for controlling the brakes associated with the wheels of a car or train in accordance with the speed of travel of the car or train and adapted also to effect an instantaneous and rapid reduction in the degree of application of the brakes associated with individual wheel units when slipping of the wheels of such wheel units occur for the purpose of preventing the sliding of the wheels.

It will be seen that I have disclosed also a novel governor device including a pump for supplying mercury to two vertically extending tubes to a level corresponding to the speed of rotation of a vehicle wheel or wheel unit. The height of the mercury column in one tube is adapted to rise and fall at all times substantially in accordance with the rotational speed of the corresponding wheel unit whereas the height of the mercury column in the other tube is prevented from rising or falling at a rate exceeding a certain rate less than that permissible in the said one tube.

As long as both mercury columns fall in unison, the governor device operates solely as a speed governor to control the degree of application of the brakes on the car or train in accordance with the speed of the vehicle. If the wheels begin to slip the mercury column in the said one tube falls more rapidly than that in the other tube and such disparity in the height of the mercury columns in the two tubes is arranged to cause an instantaneous and rapid reduction in the degree of application of the brakes associated with the corresponding wheel unit which ceases when the two mercury columns are again at the same height.

It will also be seen that I have provided a novel arrangement for reducing the degree of application of the brakes on. a car or train in accordance with the reduction in the speed of travel of the car or train to a certain low value and then, after the car or train has come to a complete stop, eifooting automatically an increase in the degree of application of th brakes to a certain higher degree.

Having now described my invention, what I claim as new and desire to secure by Letters Patent, is:

1. In a vehicle brake control apparatus of the type having means under the control of the operator for controlling the degree of application and the release of the brakes associated with all wheels of the vehicle, the combination of means for varying the degree of application of the brakes associated with all wheels of the vehicle in unison. independently of the operator, means effective during an application of the brakes independently of the operator to effect a reduction in the degree of application of the brakes associated with an individual wheel unit and the reapp icat in of the brakes thereon, and a governor device associated with each wheel unit of the vehicle, said governor device comprising two vertiallv extending tubes and a pump driven at a ed corresponding to the rotational speed of the corresponding wheel unit for causing a liquid to rise or fall in said tubes to a level correspending to the rotational speed of the wheel unit, means for limiting the rate of change of level of the liquid in one of said tubes to a certain rate lower than the possible rate of change of level of liquid in the other tube, and means effective as long as the levels of the liquid in the two tubes of one of said governor devices falls in unison for controlling the first said control to sheet a reduction in the degree of application of the brakes associated with all wheels the vehicle, and means effective when the liquid in the said one tube of each of said governor devices falls at a lesser rate than that of the other tube for effecting operation of the corresponding second control means to efiect a reduction in the degree of application of the brakes associated with the corresponding wheel unit.

2. In a vehicle brake control equipment of the type having a pipe chargeable to diiTerent fluid pressures to select the degree of application of the brakes on the vehicle, a variably conditionable relay valve device responsive to the pressure in said pipe for supplying fluid to effect application of the brakes at a pressure having a varying ratio to the pressure in the said pipe depending upon the condition of the valve device, and valve means for each of a plurality of wheel units of the vehicle normally efiective to permit the supply of fluid under pressure to effect application of the brakes associated with the wheel unit and operative to a position for preventing such supply and releasing fluid under pressure to effect the release of the brakes, the combination of a governor device for each of a plurality of Wheel units of the vehicle and having a pump driven according to the rotational speed of the corresponding wheel unit and two vertically extending tubes in which liquid is caused to rise and fall to a level corresponding to the rotational speed of the wheel unit under the influence of said pump, means for preventing the change in the level of the liquid in one of said tubes at a rate higher than a certain rate which is lower than the possible rate of change of level of liquid in the other tube, means eifective as long as the columns of liquid in the two tubes of one of said governor devices fall in unison for efiecting variation in the condition of the relay valve device in a manner to effect successive reductions in the pressure of the fluid supplied to effect application of the brakes as the speed of the vehicle reduces, and means associated with each governor device effective when the liquid column in the said one tube of the corresponding governor falls at a lesser rate than that in the other tube for efiecting operation of the corresponding said valve means to effect a reduction of the pressure of the fluid supplied to eilect application of the brakes on the corresponding wheel unit.

3. A vehicle brake control apparatus of the type having means under the control of the operator for controlling the degree of application of the brakes and the release of the brakes associated with the wheels of the vehicle, the combination of means responsive to the speed of rotation of a Wheel of the vehicle and effective during an application of the brakes initiated by the operator to effect a plurality of successive reductions in the degree of application of the brakes associated with the vehicle wheels to a certain low degree, and means responsive to the complete stopping of the vehicle for automatically increasing the degree of application of the brakes to a value higher than said certain low degree.

4 In a vehicle brake control apparatus of the type having means under the control of the operator for controlling the degree of application of the brakes and the release thereof, the combination of brake control means for varying the degree of application of the brakes independently of the operator, means responsive to the rotational speed of a wheel of the vehicle for effecting operation of said brake control means to reduce the degree of application of the brakes associated with the vehicle wheels, as the speed of vehicle reduces, to a certain minimum degree, said speed responsive means being effective when the vehicle is completely stopped for so controlling said brake control means as to efiect an increase in the degree of application of the brakes above said certain minimum degree.

5. In a vehicle brake control apparatus of the type having a pipe chargeable to different pressures to select the degree of application of the brakes associated with the vehicle wheels and effect the release thereof, and a relay valve device having a plurality of electroresponsive means energizable and deenergizable in a plurality of diiierent selected combinations whereby to variably condition the relay valve device, said relay device being operative to supply fluid at any one of a plurality of different pressures in response to a given pressure in said pipe depend ing upon the condition thereof, the combination of a governor device having a pump driven according to the rotational speed of the wheel of the vehicle and a vertically extending tube into which liquid is raised to a level varying substantially in accordance with the rotational speed of the wheel in response to the force exerted by said pump, said tube having a plurality of vertically spaced contacts adapted to be engaged by the liquid within the tube, and means whereby the energization and deenergization of the electroresponsive means for the relay valve device is controlled in response to the engagement or disengagement of the contacts in the tube by the liquid within the tube.

6. In a vehicle brake control apparatus of the type having means under the control of the operator for effecting application and release of the brakes associated with the vehicle wheel, the combination of a plurality of electro-responsive means energizable and deenergizable in any one of a plurality of different selected combinations for varying the degree of application of the brakes in accordance with the combination established, a vertically extending tube having a plurality of vertically spaced contacts adapted to be engaged by liquid rising and falling Within the tube, a pump operated in accordance with the rotational speed of a Wheel of the vehicle for causing the liquid in said tube to rise and fall to a height corresponding substantially to the rotational speed of the Wheel, and circuit means connecting said electroresponsive means and said contacts Whereby the engagement and disengagement of the liquid within the tubes with the contacts controls energization and deenergization of corresponding ones of said electroresponsive means.

'7. In a vehicle brake control apparatus of the type having means under the control of the operator for eifecting application and release of the brakes associated with the vehicle Wheels, the combination of a plurality of electroresponsive means energizable and deenergizable in any one of a plurality of selected different combinations and efiective to cause application of the brakes to a diiferent degree for each combination, a vertically extending tube having a plurality of vertically spaced contacts adapted to be engaged or disengaged by a current-conducting liquid within the tube according to the level of the liquid within the tube, a pump operated in accordance with the rotational speed of the Wheel of a vehicle for impelling liquid to a height within the tube corresponding substantially to the rotational speed of the Wheels, and means connecting said contacts to said electroresponsive means in such a manner as tocause a reduction in the degree of application of the brakes to a certain minimum degree at a time that the level of the liquid in the tube descends below the next to the lowest contact and effective to so control the electroresponsive means as to cause an increase in the degree of application ol the brakes above said certain minimum degree when the level of the liquid in the tube descends below the lowest of the contacts.

8. Vehicle brake control apparatus comprising the combination of a vertically extending tube having a plurality of vertically spaced contacts adapted to be engaged by current-conducting liquid rising and falling within the tube, a pump operated in accordance with the rotational speed of a wheel of the vehicle for impelling liquid to a height within said tube substantially in proportion to the rotational speed of the wheel, and means controlled according to the cooperation of the liquid within the tube with the vertically spaced contacts for controlling the degree of application of the vehicle brakes.

9. Vehicle brake control apparatus comprising the combination of a vertically extending tube having a plurality of vertically spaced contacts adapted to be engaged by a current-conducting liquid rising and falling within the tube, a pump operated in accordance with the rotational speed of a wheel of the vehicle for causing the said liquid to rise and fall within the tubes in accordance with variations in the rotational speed of the wheel, the lowest of said contacts being so positioned that the liquid within the tube falls therebelow only at the time the vehicle comes to a complete stop, and brake control means controlled in accordance with the engagement of the liquid within the tube with the said contacts for effecting a reduction in the degree of application of the brakes associated with the vehicle wheels to a certain minimum degree as long as the liquid in the tubes remains above said lowest contact and adapted to effect an increase in the degree of application of the brakes when the liquid in the tube descends below said lowest contact.

10. In a vehicle brake control apparatus of the type having a brake cylinder to which fluid under pressure is supplied and released under the control of the operator for effecting the application and release of the brakes associated with a wheel of the vehicle, and control means operative to prevent the supply of fluid under pressure to the brake cylinder and efiect the release of fluid under pressure therefrom, the combination of two vertically extending tubes, a pump operated in accordance with the rotational speed of the wheel for causing liquid to rise or fall within said tube to a height corresponding substantially to the rotational speed of the wheel,

means for restricting the fall of the liquid in one of said tubes to a rate less than a certain rate whereby upon deceleration of the vehicle wheel at a rate exceeding a corresponding rate the level of the liquid in the said one tube falls at a lesser rate than the level of liquid in the other tube, and means effective upon the occurrence of a predetermined difierence in the levels of the liquid in the two tubes throughout the height of said tubes for eflecting operation of said control means.

11. In a vehicle brake control apparatus of the type having means under the control of the operator for effecting application and release of the brakes associated with the vehicle wheels, the combination compr sing two vertically extending tubes, a pump for causing liquid to rise or fall within the tubes to a height corresponding substantially to the rotational speed of a wheel of the vehicle, means for restricting the rate of fall of liquid in one of said tubes to a rate less than that permitted in the other of said tubes whereby when the vehicle wheel rotatively decelerates at a rate exceeding a certain slipping rate, the liquid in the said other tube falls at a faster rate than that in the said one tube, brake control means controlled according to the level of the liquid in the said one tube for effecting a graduated reduction in the degree of application of the brakes associated with all wheels of the vehicle as the speed of the vehicle reduces, and means responsive to a predetermined differential in the level of the liquids in the two tubes for effecting a rapid reduction in the degree 0! application of the brakes associated with a limited number of the wheels including said wheel.

12. In a vehicle brake control apparatus of the type having means under the control of the operator for efiecting application and release of the brakes associated with the vehicle wheels, the combination comprising two vertically extending tubes, a pump for causing liquid to rise or fall within the tubes to a height corresponding substantially to the rotational speed of a Wheel of the vehicle, means for restricting the rate of fall of liquid in one of said tubes to a rate less than that permitted in the other of said tubes whereby when the vehicle wheel rotatively decelerates at a slipping rate the liquid in the certain other tube falls at a rate faster than that in the said one tube, and brake control means controlled in part according to the level of the liquid in said one tube and in part in accordance with the difference in the levels of the liquids in the two tubes.

EVERETT P. SEXTON. 

